Weeks 7–10 — Dictionaries & Sets · String Methods & Formatting · Functions · Basic Capstone: CLI To-Do App

phonebook = {}
while True:
    cmd = input("add/lookup/delete/quit: ").strip()
    if cmd == "add":
        name = input("  Name: ")
        phone = input("  Phone: ")
        phonebook[name] = phone
        print(f"  Saved {name}.")
    elif cmd == "lookup":
        name = input("  Name: ")
        print(" ", phonebook.get(name, "Not found"))
    elif cmd == "delete":
        name = input("  Name: ")
        phonebook.pop(name, None)
    elif cmd == "quit":
        break

text = input("Enter a sentence: ").lower()
words = text.split()
freq = {}
for w in words:
    freq[w] = freq.get(w, 0) + 1
for word, count in sorted(freq.items(), key=lambda x: -x[1]):
    print(f"  {word}: {count}")

a = set("the cat sat on the mat".split())
b = set("the dog sat on the log".split())
print("Common words:  ", a & b)
print("Unique to A:   ", a - b)
print("All words:     ", a | b)

Common words:   {'the', 'on', 'sat'}
Unique to A:    {'cat', 'mat'}
All words:      {'the', 'on', 'sat', 'cat', 'mat', 'dog', 'log'}

raw = "  python is AWESOME!  "
cleaned = raw.strip().lower()
print(cleaned)
print(cleaned.count("is"))
print(cleaned.replace("python", "coding"))

python is awesome!
1
coding is awesome!

line = "Alice,25,Seoul,Developer"
fields = line.split(",")
labels = ["Name", "Age", "City", "Job"]
for label, value in zip(labels, fields):
    print(f"{label:6}: {value}")

Name  : Alice
Age   : 25
City  : Seoul
Job   : Developer

students = [("Alice", 95), ("Bob", 82), ("Charlie", 71)]
print(f"{'Name':<10} {'Score':>6}")
print("-" * 18)
for name, score in students:
    print(f"{name:<10} {score:>6}")

Name        Score
------------------
Alice           95
Bob             82
Charlie         71

def add(a, b): return a + b
def sub(a, b): return a - b
def mul(a, b): return a * b
def div(a, b): return a / b if b else "Error: division by zero"

a = float(input("a: "))
b = float(input("b: "))
print(f"  +: {add(a,b)}")
print(f"  -: {sub(a,b)}")
print(f"  *: {mul(a,b)}")
print(f"  /: {div(a,b)}")

def mean(lst):
    return sum(lst) / len(lst)

def variance(lst):
    m = mean(lst)
    return sum((x - m)**2 for x in lst) / len(lst)

def std_dev(lst):
    return variance(lst) ** 0.5

data = [10, 20, 30, 40, 50]
print(f"Mean:    {mean(data):.2f}")
print(f"Std Dev: {std_dev(data):.2f}")

Mean:    30.00
Std Dev: 14.14

def factorial(n):
    """Return n! recursively."""
    if n <= 1:
        return 1
    return n * factorial(n - 1)

for i in range(1, 8):
    print(f"{i}! = {factorial(i)}")

1! = 1
2! = 2
3! = 6
4! = 24
5! = 120
6! = 720
7! = 5040

import json, os

FILE = "tasks.json"

def load_tasks():
    if os.path.exists(FILE):
        with open(FILE) as f:
            return json.load(f)
    return []

def save_tasks(tasks):
    with open(FILE, "w") as f:
        json.dump(tasks, f, indent=2)

def add_task(tasks, title):
    task_id = max((t["id"] for t in tasks), default=0) + 1
    tasks.append({"id": task_id, "title": title, "done": False})
    print(f"  [{task_id}] added.")

def list_tasks(tasks):
    if not tasks:
        print("  No tasks.")
        return
    print(f"  {'ID':<4} {'Status':<8} Title")
    for t in tasks:
        status = "[x]" if t["done"] else "[ ]"
        print(f"  {t['id']:<4} {status:<8} {t['title']}")
    done = sum(1 for t in tasks if t["done"])
    print(f"  Done: {done}/{len(tasks)}")

def mark_done(tasks, task_id):
    for t in tasks:
        if t["id"] == task_id:
            t["done"] = True
            print(f"  [{task_id}] marked as done.")
            return
    print(f"  Task {task_id} not found.")

def delete_task(tasks, task_id):
    orig = len(tasks)
    tasks[:] = [t for t in tasks if t["id"] != task_id]
    if len(tasks) < orig:
        print(f"  [{task_id}] deleted.")
    else:
        print(f"  Task {task_id} not found.")

def main():
    tasks = load_tasks()
    print("Todo App — type 'help' for commands")
    while True:
        line = input("> ").strip()
        if not line:
            continue
        parts = line.split(maxsplit=1)
        cmd = parts[0].lower()
        arg = parts[1] if len(parts) > 1 else ""
        if cmd == "add":
            if arg:
                add_task(tasks, arg)
                save_tasks(tasks)
            else:
                print("  Usage: add <title>")
        elif cmd == "list":
            list_tasks(tasks)
        elif cmd == "done":
            try:
                mark_done(tasks, int(arg))
                save_tasks(tasks)
            except ValueError:
                print("  Usage: done <id>")
        elif cmd == "delete":
            try:
                delete_task(tasks, int(arg))
                save_tasks(tasks)
            except ValueError:
                print("  Usage: delete <id>")
        elif cmd in ("quit", "exit"):
            print("  Bye!")
            break
        elif cmd == "help":
            print("  Commands: add <title>, list, done <id>, delete <id>, quit")
        else:
            print(f"  Unknown command: {cmd}")

if __name__ == "__main__":
    main()